Muamba's heart had stopped for 78 minutes following his collapse during the FA Cup quarterfinal against Tottenham at White Hart Lane on 17 March.
The 23-year-old, who was rushed to the London Chest Institute and has been described as being in critical condition since then, finally got out of bed for the first time since the incident and has also started to eat. He remains in intensive care but his condition is stable.
"Very happy and extremely relieved. Just learned from the chairman of Bolton that Fabrice Muamba is on the mend. Dear Fabrice, get well soon. The world of football is with you and keeps its fingers crossed," Blatter said on Twitter.